I had to make my own burlap sacks. The reason - the ones you find in stores in the craft departments have very loose weave. The weave is too loose and the seeds will go right through them. So I purchased a yard and made my own from a tighter weave.
Now...there are some places that you can find burlap feed bags from time to time. But they are Huge so you need to cut them and sew anyway. The nice thing about purchasing it and doing your own is that you can get plain burlap that hasn't been treated with chemicals at most fabric stores so you know exactly what you're getting. You also make them an appropriate size for the number of birds you're feeding.
I get my grains at the feed mill and use whatever is the best price at the time. Usually barley, oats. Sometimes wheat but it is often a very high price depending on the crop at the time.
You'll find that the birds will not want to eat sprouted beans/legumes. And many of them are toxic to birds and shouldn't be fed to them anyhow so I recommend you just stick with grains, sunflower seed and the like. Even some grains need to be fed in moderation as they can have various side effects.
Take a quick look at the "grains" and "protein" links on this page:
http://www2.ca.uky.edu/smallflocks/Nutrition.html
As you go through each grain it will state various reasons not to feed some and to restrict others.
When it comes to legumes for chickens, some of them are toxic in any form and some must be roasted to at least reduce toxcicity (which would tell you that no chicken would ever eat them if they had a choice as I've never seen a chicken build a fire and roast anything...at least mine don't...)
There are things listed on that site that I would never feed my birds. So that is my disclaimer - I only post it so that you can get an idea of what things should be avoided.